The ERG and VEP are commonly used tools for diagnosing abnormalities of visual pathways. Their usefulness has been severely restricted, however, by their limited information content. This study proposes to develop and test a new methodology (called "markov kernels" which could greatly enhance the role of the ERG and VEP in the clinic. Markov kernels are rich in information content and yet have the ease of interpretability of conventional flash responses. They also have major signal-to-noise advantages over other rapid stimulus techniques. All our proposed experiments will use two independent, rapidly fluctuating stimuli to selectively explore particular sources of interactions in the visual pathways. We will measure color interactions, binocular interactions and spatial interactions. For illustration, suppose th etwo stimuli were different colors. Particular Markov kernels would contain information on how the response to a flash of one color was modified by a flash of the same or different color which preceded it at a specific time in the same or opposite eye. Our goal is to develop a powerful clinical tool: 1. The spatial and temporal properties of our stimuli will be designed to enhance responses from intermediate stages of the visual pathway (ganglion cells and LGN). Responses from intermediate structures in auditory and somatosensory EPs have proven useful in localizing lesions in those neural systems. 2. The testing will be rapid and variability will be minimized because multiple visual functions will be tested simultaneously under identical conditions. 3. Immediate feedback from the on-line computer is important for the clinic where rapid decisions must be made about what further tests are needed. The above studies are pilot projects because the Markov techniques and the interaction techniques are too new to have been tested yet. Techniques for enhancing the ERG pattern response and the VEP brainstem response are still being developed. Prior to the Markov method clinical data were too noisy to give satisfactory higher order kernels, so pilot studies are needed to explore where the new techniques can be particularly useful.